A patent document 1 discloses a socket for a temporal connection of a ball grid array (BGA) integrated circuit device to a test circuit. The socket includes a pattern of contacts corresponding to a pattern of terminals, e.g., solder balls provided on a bottom surface of the integrated circuit device. Each of the contacts has a pair of tips for resiliently nipping an associated one of the solder balls of the integrated circuit device. The socket also has structures for moving each pair of contact tips between an opened position in which the contact tips are spaced apart from each other to accommodate the associated solder ball therebetween and a closed position in which the contact tips resiliently hold the associated solder ball therebetween.
A patent document 2 discloses another socket including one or more pairs of retainers for forcing the integrated circuit device against the contacts to attain reliable contacts between the contacts of the socket and the associated solder balls of the integrated circuit device. Each of the retainers is supported for rotation between a protruded position in which each of the retainers is protruded above the upper surface of the integrated circuit to force the integrated circuit device against the contacts and a retracted position in which the retainer is fully retracted from above the integrated circuit device. A spring is provided for each retainer to force the retainer toward the protruded position.
The sockets have various advantages. Among other things, the retainers ensure reliable electrical contacts between the solder balls of the integrated circuit device and the associated contacts of the socket. However, when optically checking whether a sufficient opening or gap necessary for receiving the solder ball is formed between the opened contact tips and/or whether a predetermined physical condition is provided to each contact, the protruded retainers can intervene between the camera and a part of the contacts, inhibiting the measurement of the gaps of those contacts, depending upon the size and/or shape of the retainers. This requires that the retainers are retained in the retracted positions by means of exclusively designed tools before mounting the socket onto the test site. Also, a fitting and unfitting of the tool requires an extra effort and time.
In view of foregoing, a purpose of the present invention is to provide a socket, a socket base and methods for operating and testing the sockets, capable of holding the retainers outside the viewing field of the camera in spite of the size and/or shape of the retainers.